The present invention relates to an apparatus and method for controlling the application of liquid substances such as wax and fungicides to surfaces of fruit such as citrus fruit, apples and other fruit where is is desirable to apply a uniform coating over the surface of the fruit for appearance enhancement, decay control, and sporulation control. The liquid substances may comprise an aqueous or solvent solution of various resins or mixtures and of resins and wax emulsions, together with selected fungicidal compositions.
A prior proposed apparatus and method of treating fruit is described in U.S. Pat. No. 2,898,881 issued Aug. 11, 1959, owned by the assignee of this application, in which a liquid wax was sprayed on surfaces of fruit by an atomizing nozzle which was reciprocally moved in two parallel paths transversely of the direction of movement of the fruit on a brush roll conveyor. The nozzle was uniformly spaced above the conveyor and sprayed the liquid wax over a treating zone through which the fruit was passed and agitated to expose virtually all of the surface of the fruit to the spray. In one example in the patent two nozzles were employed in the transverse treating zone, each nozzle being carried by a separate sprocket and chain and reciprocally moved through the transverse spray zone. In this patented apparatus, the rapidity of oscillation of the nozzles was directly correlated to the linear rate of advancement of the fruit along the brush roll conveyor and the size of the nozzle means was selected to operate under a given pressure so that the cone shaped spray pattern caused forcible impingement of the atomized liquid wax against the fruit surfaces.
Other prior proposed apparatuses and methods for spraying of aqueous and non-aqueous liquid substances on fruit have included arrays of fixed nozzles of selected size and operable at selected pressures to direct an atomized spray against the surfaces of fruit as the fruit passed thereunder on a brush roll conveyor.
In such prior proposed apparatuses for application of liquid substances to fruit surfaces, the amount of liquid substance discharged from the spray nozzles was predetermined and was discharged from the nozzle even though the amount of fruit on the brush roll conveyor substantially varied in quantity. In addition, the speed of the conveyor for the fruit while desirably set for a selected speed, was often varied in order to attempt to assure that the brush roll conveyor was substantially filled or covered with a maximum amount of fruit. Feeding of fruit to such a conveyor was often at a nonuniform rate and the speed of the brush roll conveyor might be manually modified. The amount of liquid substance discharged by the nozzles during reciprocation might be varied by manually modifying the pump speed to change the rate of flow and also the fluid pressure in order to seek a more uniform and effective distribution of the sprayed liquid substance. However, manual adjustment of pump sppeed, rate of flow, pressure, conveyor speed, and rate of nozzle reciprocation made the desired results of uniform consistent gloss or shine on the fruit surface, uniform fungicide protection, reduced wax buildup on equipment, and improved wax consumption difficult to achieve.
It will be apparent that when a brush roll conveyor was not carrying a maximum quantity of fruit that in the absence of certain quantities of fruit the amount of spray discharged remained substantially the same and as a result was discharged not principally upon fruit surfaces but upon the brush rolls and resulted in an unwanted accumulation of liquid substance or wax on the conveying brush rolls. Periodic shut down of the apparatus was required to permit cleaning of excess waxy substances from the brush roll conveyor. Further, application of wax by the nozzles to vacant area portions of the brush roll conveyor was essentially a waste of the liquid wax and contributed to rapid buildup of wax.